16 Aug 2018

Baggio S et al. Front Psychiatry 2018; 9: 331

A significantly higher prevalence of ADHD has been reported in incarcerated populations compared with the general population. A previous meta-analysis, which included studies published until 2012, identified a five- to ten-fold increase in the prevalence of ADHD in incarcerated populations compared with the general population (Young et al. 2015). The current meta-analysis aimed to provide an updated estimate of the ADHD prevalence rate for people living in detention over the past three decades, including articles published since 2012.

The authors conducted a systematic review and meta-analysis following the Preferred Reporting Item for Systematic Reviews and Meta-Analyses (PRISMA) and the Meta-analysis of Observational Studies in Epidemiology (MOOSE) checklists. Databases including PubMed/Medline, PsycINFO and Web of Science were searched, combining “ADHD” and “prison” keywords and synonyms for articles published between 1 January 1966 and 2 January 2018. Studies investigating people living in detention were eligible for inclusion if they (i) reported an empirical study, (ii) were written in English and (iii) were published in a peer-reviewed journal. Following two rounds of selection and data extraction, articles were assessed for the risk of bias using an adaptation of the Quality in Prognosis Studies. Next, the meta-analytic ADHD prevalence rate was estimated, and potential sources of variation were investigated using meta-regressions and subgroup analyses. Covariates that were assessed included region, gender, study population (adults/youths), psychiatric diagnosis (yes/no), serious offender (yes/no), diagnostic approach (interview/screening/retrospective screening), Diagnostic and Statistical Manual of Mental Disorders (DSM) version (DSM-III/DSM-IV/DSM-5TM) and quality of data (strong/moderate/weak).

This meta-analysis pooled 102 original studies and included 69,997 participants (males: 89%; females: 11.0%; adults: 27.5%, mean age 32.7 years, range 24.8–44.9 years; youths: 72.5%, mean age 16.4 years, range 14.0–20.0 years).* The majority of studies (64.7%) were published between 2008 and 2017. Data came from 28 countries, including those in Europe (49.0%), North America (35.3%), Asia (6.9%), Australia (4.9%) and South America (3.9%). Most studies used a clinical diagnosis of ADHD (58.5%), although 21.1% and 20.4% used self-reported screenings of childhood ADHD and adolescent/adult ADHD, respectively. Overall, the quality of the studies was high; however, ‘weak’-quality studies contributed towards 23.2% of the sample.†

The overall prevalence rate for adolescent/adult ADHD was estimated at 26.2% (95% confidence interval [CI] 22.7–29.6). Data based on clinical interviews only showed a similar ADHD prevalence rate of 26.7% (95% CI 22.7–30.7). Retrospective assessments of ADHD in childhood were associated with a significantly increased prevalence of 41.1% (95% CI 34.9–47.2). Meta-regression analysis demonstrated that prevalence estimates pooled from studies using self-reported screening for adolescent/adult ADHD were not statistically different from estimates from studies using clinical interviews (i.e. for the univariate model: respectively, b = 0.028, which corresponded to a prevalence estimate of 0.28 + 0.15 = 43%; p < 0.001). Conversely, screenings of childhood ADHD were associated with an increased prevalence rate compared with clinical interviews (i.e. for the univariate model: respectively, b = 0.028, which corresponded to a prevalence estimate of 0.28 + 0.15 = 43%; p < 0.001). No other covariates were associated with heterogeneity of prevalence estimates.

This meta-analysis was limited by a number of factors. First, most studies did not report ADHD treatment, which may have been useful in understanding ADHD remission. Second, although the meta-analysis took into account the overall diagnostic approach, the variation in the validity and reliability of ADHD assessments may have contributed to the heterogeneity of results. Finally, there were few studies that applied the DSM-5™ definition of ADHD for meaningful analysis, and some regions of the world were under-represented (South America), whereas others were not represented at all (e.g. Africa).

This meta-analysis provided an updated prevalence estimate of ADHD in prison settings, including people living in detention confined to psychiatric units. The pooling of all studies yielded an adolescent/adult ADHD prevalence rate of 26.2%, whilst the pooling of studies using clinical interviews only demonstrated a similar prevalence rate of 26.7%. This corresponded with a five-fold increase in ADHD prevalence rates among incarcerated people compared with the general population. The authors concluded that these findings were consistent with previous reports (Polanczyk et al. 2014; Willcutt 2012; Ramos-Quiroga et al. 2014), reinforcing the importance of offering ADHD screening and diagnosis for all individuals entering detention, and delivering treatment for ADHD to individuals both whilst they are in prison and after their release.

*916 records were identified during the literature search. 223 records were removed due to duplication and 527 records were excluded as they did not meet the inclusion criteria. After the second review round, a further 81 publications were excluded: 23 articles did not report ADHD prevalence or gender-disaggregrated prevalence rates; 8 used samples in which 100% of participants had ADHD; 47 relied on data already used in other articles; and 3 were not accessible by the authors. A manual search of published meta-analyses led to the identification of 17 additional studies, which resulted in a total of 102 publications and 142 samples included in the meta-analysis: 67 studies with a single sample; 26 studies including both genders; 9 studies with two assessment tools; one study including both genders and two diagnostics; and one study with three diagnostics (one childhood screening, one adulthood screening, and a clinical interview)†Of the ‘weak’-quality studies, 13.4% had a response rate of ≤60% or a convenient sample, 24.7% excluded non-native speakers and 16.2% excluded people living in detention with psychiatric or somatic disorders

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